fgdata/gui/dialogs/chat.xml

<?xml version="1.0"?>

<PropertyList>
  <name>chat</name>
  <modal>false</modal>
  <layout>vbox</layout>

  <group>
    <layout>hbox</layout>

    <input>
     <name>compose</name>
     <pref-width>500</pref-width>
     <stretch>true</stretch>
     <halign>fill</halign>
     <length>50</length>
     <property>/sim/multiplay/chat-compose</property>
    </input>

    <button>
      <legend>Send</legend>
      <default>true</default>
      <key>Enter</key>
      <binding>
        <command>dialog-apply</command>
      </binding>
      <binding>
        <command>nasal</command>
        <script>
          var lchat = getprop("/sim/multiplay/chat-compose");
          if (lchat != "")
          {
            setprop("/sim/multiplay/chat", lchat);
            setprop("/sim/multiplay/chat-compose", "");
            gui.dialog_update("chat", "compose");
          }
        </script>
      </binding>
    </button>
  </group>


  <group>
    <layout>hbox</layout>
    <empty><stretch>true</stretch></empty>

    <button>
      <legend>Close</legend>
      <default>true</default>
      <key>Esc</key>
      <binding>
        <command>dialog-close</command>
      </binding>
    </button>

    <button>
      <legend>More v</legend>
      <default>false</default>
      <binding>
       <command>dialog-show</command>
       <dialog-name>chat-full</dialog-name>
      </binding>
      <binding>
        <command>dialog-close</command>
      </binding>
    </button>

    <empty><stretch>true</stretch></empty>
  </group>
</PropertyList>